I organise through colour - so a separate coloured binder for each subject. Then a matching notebook or slip file for each subject.
For text books I have a different coloured highlighter or post it note for things like quotes, sources, terminology etc.
Flash cards just elastic bands do the trick.
A diary - day to a page is a must for your todo list, count down for important dates, homework due etc.
Get one place and put your studies in the place, so all your binders, text book and stationery. This helps you concentrate.
It doesn’t have to be fancy, it can just be a concertina file or a desk tray. It’s about building a system that works for you.